From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, T_DKIMWL_WL_HIGH,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1CD6EC04AB1 for ; Thu, 9 May 2019 18:54:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E7B5F204FD for ; Thu, 9 May 2019 18:54:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557428054; bh=k/TeH7BaKVX1u50l//zvo0KDlOFkKEQ+Vt+mzlbxyaU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=kgZBkxY/myhzvT7Ml8GuOxyNcJcOeJsoiJ0rGw8p0v2wX0BEPUzIHU535gNu6Pro/ 4GkdFATFZoK8ddE/wVbs1MBheZeH3QAohpTjmYoJpEBzuDLeftZ2RgOOMSxM9qzNOt OzY3oiC/ZbEmepC/ep0hAycPBn2utHT6GBwT6K0g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727888AbfEISyM (ORCPT ); Thu, 9 May 2019 14:54:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:48800 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728749AbfEISyI (ORCPT ); Thu, 9 May 2019 14:54:08 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 432DF2177E; Thu, 9 May 2019 18:54:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557428047; bh=k/TeH7BaKVX1u50l//zvo0KDlOFkKEQ+Vt+mzlbxyaU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yKQqLticbjJAzqMEqmJ5E13XuMNUFZP3F4OFzq52x/J/VtuuasTF3F+XQ27acIlCc JzivhFOpWQpcfschntm0bEV83ZyZNDovYjow5G0DSmQS3J0VqFlqF75DrzVmYnacjd 705XkVENIAiCx7VhP6PGEsqDCkXZn+OjHLYeEGFU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Johan Hovold , Oliver Neukum Subject: [PATCH 5.0 77/95] USB: cdc-acm: fix unthrottle races Date: Thu, 9 May 2019 20:42:34 +0200 Message-Id: <20190509181314.737330384@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190509181309.180685671@linuxfoundation.org> References: <20190509181309.180685671@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Johan Hovold commit 764478f41130f1b8d8057575b89e69980a0f600d upstream. Fix two long-standing bugs which could potentially lead to memory corruption or leave the port throttled until it is reopened (on weakly ordered systems), respectively, when read-URB completion races with unthrottle(). First, the URB must not be marked as free before processing is complete to prevent it from being submitted by unthrottle() on another CPU. CPU 1 CPU 2 ================ ================ complete() unthrottle() process_urb(); smp_mb__before_atomic(); set_bit(i, free); if (test_and_clear_bit(i, free)) submit_urb(); Second, the URB must be marked as free before checking the throttled flag to prevent unthrottle() on another CPU from failing to observe that the URB needs to be submitted if complete() sees that the throttled flag is set. CPU 1 CPU 2 ================ ================ complete() unthrottle() set_bit(i, free); throttled = 0; smp_mb__after_atomic(); smp_mb(); if (throttled) if (test_and_clear_bit(i, free)) return; submit_urb(); Note that test_and_clear_bit() only implies barriers when the test is successful. To handle the case where the URB is still in use an explicit barrier needs to be added to unthrottle() for the second race condition. Also note that the first race was fixed by 36e59e0d70d6 ("cdc-acm: fix race between callback and unthrottle") back in 2015, but the bug was reintroduced a year later. Fixes: 1aba579f3cf5 ("cdc-acm: handle read pipe errors") Fixes: 088c64f81284 ("USB: cdc-acm: re-write read processing") Signed-off-by: Johan Hovold Acked-by: Oliver Neukum Cc: stable Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- drivers/usb/class/cdc-acm.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-) --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -470,12 +470,12 @@ static void acm_read_bulk_callback(struc struct acm *acm = rb->instance; unsigned long flags; int status = urb->status; + bool stopped = false; + bool stalled = false; dev_vdbg(&acm->data->dev, "got urb %d, len %d, status %d\n", rb->index, urb->actual_length, status); - set_bit(rb->index, &acm->read_urbs_free); - if (!acm->dev) { dev_dbg(&acm->data->dev, "%s - disconnected\n", __func__); return; @@ -488,15 +488,16 @@ static void acm_read_bulk_callback(struc break; case -EPIPE: set_bit(EVENT_RX_STALL, &acm->flags); - schedule_work(&acm->work); - return; + stalled = true; + break; case -ENOENT: case -ECONNRESET: case -ESHUTDOWN: dev_dbg(&acm->data->dev, "%s - urb shutting down with status: %d\n", __func__, status); - return; + stopped = true; + break; default: dev_dbg(&acm->data->dev, "%s - nonzero urb status received: %d\n", @@ -505,10 +506,24 @@ static void acm_read_bulk_callback(struc } /* - * Unthrottle may run on another CPU which needs to see events - * in the same order. Submission has an implict barrier + * Make sure URB processing is done before marking as free to avoid + * racing with unthrottle() on another CPU. Matches the barriers + * implied by the test_and_clear_bit() in acm_submit_read_urb(). */ smp_mb__before_atomic(); + set_bit(rb->index, &acm->read_urbs_free); + /* + * Make sure URB is marked as free before checking the throttled flag + * to avoid racing with unthrottle() on another CPU. Matches the + * smp_mb() in unthrottle(). + */ + smp_mb__after_atomic(); + + if (stopped || stalled) { + if (stalled) + schedule_work(&acm->work); + return; + } /* throttle device if requested by tty */ spin_lock_irqsave(&acm->read_lock, flags); @@ -842,6 +857,9 @@ static void acm_tty_unthrottle(struct tt acm->throttle_req = 0; spin_unlock_irq(&acm->read_lock); + /* Matches the smp_mb__after_atomic() in acm_read_bulk_callback(). */ + smp_mb(); + if (was_throttled) acm_submit_read_urbs(acm, GFP_KERNEL); }